This invention relates generally to telephone circuit test instruments and, more particularly, to such instruments that are portable in nature and which also include telephone circuit supervising and controlling means.
The testing of telephone circuits for transmission quality is a common practice in the maintenance of a telephone system. Such testing is most often conducted in a telephone central office, both upon its own circuits and those connecting the central office with another location. A test apparatus having a test signal transmitter and a receiver permits the testing of transmission characteristics of a line by inserting the test apparatus at one end of the line and looping the other end back upon itself. The test signal transmitted by the testing apparatus travels along such a circuit to its end and back again to the test apparatus receiver where a measurement is made. A test signal transmitter can be a white noise generator, pure sine wave generator, etc., while a receiver of the test set and associated measuring circuitry detects some characteristic of the transmitted signal after passing through the communication circuit under test. A particular characteristic that is typically measured may be the loss of 1 kHz, the frequency response of the line, its echo return loss or its singing point in any one test.
Such testing apparatus, including both a transmitter and receiver, is presently manufactured in a portable configuration. It is moved around to convenient locations within a central office for testing various telephone lines. A central telephone office usually has telephone status monitoring equipment located at centralized positions within the office. The result is that a technician using such a test set cannot be sure of the communication status of the line that he is testing unless he happens to be physically located near one of the central office test boards equipped with supervision indicators. If the testing technician is located away from such supervising stations in order to make a connection with a desired telephone line, a second technician must be employed to monitor the supervising indicators while the two technicians are in communication on some unused telephone circuit.
It is a primary object of the present invention to provide a portable telephone line testing apparatus that permits efficient and accurate telephone line testing from anywhere in a central office with reduced manpower requirements.
It is an additional object of the present invention to provide an improved telephone line supervising circuit.